A medical respiratory apparatus such as a nebuliser or humidifier commonly includes a transparent or translucent chamber, containing fluid, usually water or an aqueous solution of a medicament intended for inhalation. In use, the fluid is entrained in a flow of air or other gas which is inhaled by a patient. The level of the fluid in the chamber needs to be instantly visually identified, effectively and efficiently, by the human eye for reasons of efficient and effective operation of the apparatus and in some instances safety. For instance, it may be necessary to ensure that the level of the fluid does not fall below a prescribed minimum or rise above a prescribed maximum. However, such levels can often be indistinct or obscured due to the opaqueness of the chamber material, condensation of fluid on chamber walls, product graphics and labels, or the transparency of the fluid itself.
There have now been devised improvements to medical respiratory apparatus which overcome or substantially mitigate the above-mentioned or other disadvantages of the prior art.